1. Field of the Invention
The present invention relates to a bi-directional, non-contact face seal for sealing, from the ambient, a pressurized fluid in the interior of a housing fitted with a rotatable shaft.
2. Description of the Prior Art
The majority of seals used on rotating shafts in pressurized environments are contact seals which include a rotor fixed to the shaft and a stator fixed to the housing. In these traditional seals, when the shaft rotates, the rotor and the stator physically contact and slide relative to one another. As a result, abrasion occurs between the faces of the rotor and the stator. Such contact seals, therefore, require lubrication on or between the rubbing faces of the rotor and stator, particularly when subjected to high pressures and excessive speeds. If the sealed pressurized fluid has good lubrication qualities, the use of a contact seal structure is acceptable. However, contact seals exhibit undesirable wear characteristics and leakage, when used to seal fluids, such as air and steam, which do not have good lubrication characteristics.
In order to overcome the above difficulties, some efforts have been made to produce non-contact seals having a gap formed between the rotor and the stator to thereby eliminate rubbing. Such non-contact seals, however, represent a small percentage of conventional seals. Further, the state-of-the-art conventional non-contact seals have limited application and value. Conventional non-contact seals generally utilize spiral type grooves in the face of the rotor. An example of such seal is described in U.S. Pat. No. 4,212,475 to Sedy entitled Self Aligning Spiral Groove Face Seal. These non-contact seals are designed to function in a unidirectional manner. If the seals are driven in the opposite direction, they will not separate but will be pulled or sucked toward each other, thereby increasing wear and ultimately destroying the seal. For these reasons, the non-contact seals employing spiral grooves have significant limitations.